Hypochlorite bleaches and, more recently, peroxygen bleaching compounds, such as hydrogen peroxide, sodium percarbonate and sodium perborate monohydrate or tetrahydrate, for example, have been found useful in the bleaching of fabrics, textiles, and other similar materials.
Preformed peracid chemistry has developed more recently and been found to provide bleaching action.
Now, peracid precursor or activated bleach chemistry presents further alternative bleaching compositions. Generally, this chemistry concerns the use of precursors or activators which combine in aqueous solution with a peroxygen bleaching compound to cause effective bleaching action.
There have accordingly been a number of such peracid precursors or bleach activators developed in the prior art.
For example, U.S. Pat. No. 4,283,301 issued Aug. 11, 1981 to Diehl disclosed peracid precursors in the form of esters having different leaving groups specifically identified as either enols, imidazoles or carbon acids. In this regard, the Diehl patent is similar to many other references in using the term "leaving group" to identify a substituent of a precursor molecule which rapidly cleaves off in aqueous solution and promotes formation of the desired peracid. Diehl employed the symbol Z to designate such a leaving agent within a peracid precursor and that practice is also employed in the following disclosure of the present invention.
U.S. Pat. No. 4,412,934 issued Nov. 1, 1983 to Chung et al also disclosed surface active peracid precursors, which were denoted as "bleach activators", having the general configuration or structure RCOL wherein R was an alkyl group with 5 to 18 carbon atoms and L was a leaving group, the conjugate acid of which had a pKa in the range of 6-13. GB 864,798, however, appears to have disclosed the same technology at an earlier time.
U.S. Pat. No. 4,483,778 issued Nov. 20, 1984 to Thompson et al disclosed a modification of a peracid precursor of the Chung et al type, particularly for the purpose of reducing or eliminating undesirable odors.
European Patent Publications No. 105,672 and 105,673, both published Apr. 18, 1984 upon application by the Proctor & Gamble Company, disclosed methods of synthesizing peracid precursors of the type disclosed by Chung et a1.
U.S. Pat. No. 4,473,507 issued Sept. 25, 1984 to Bossu disclosed preformed peroxy acid bleach preferably employed in conjunction with a dry, granular, controlled release laundry bleach product in a water-permeable pouch.
All of the above noted peracid precursors or bleach activators and the peracids resulting in aqueous solution have been found to be effective to one degree or another in terms of bleaching activity.
There has been found to remain a need for peracid precursors having further improved characteristics. For example, in addition to providing increased bleaching action, it is also desirable to provide a peracid precursor capable of providing greater peracid yield in aqueous solution. At the same time, there has also been found to remain a need for new peracid precursors and corresponding methods for effectively synthesizing the precursors.